Conventionally, for example, Patent Document 1 discloses a valve operating mechanism for an internal combustion engine, which is provided with a cam carrier for each cylinder, the cam carrier being provided with two kinds of cams, and changes over a valve driving cam for each cylinder by moving the cam carrier in the axial direction with respect to the cam main axis which is driven to rotate. To be more specific, this conventional valve operating mechanism is provided with a guide groove which is formed into a helical shape on opposite ends on the outer peripheral surface of each cam carrier. Moreover, an electric actuator is provided for each guide groove for driving a drive pin which is inserted into or withdrawn from the guide groove.
According to the above described conventional valve operating mechanism, the cam carrier is displaced in its axial direction by the engagement of the drive pin with a guide groove. Since this changes over the valve driving cam of each cylinder, it is possible to change the lift amount of the valve.
It is noted that the applicant recognizes the following documents including the above described one as those relating to the present invention.